The invention has been achieved to solve the problems described above, and its object is to provide a digital VTR with which the picture quality is higher in special replay, such as slow replay, still replay and fast replay.
Another object is to improve the resolution during fast replay.
A further object of the invention is to provide a digital VTR with which a fast replay signal can be reproduced without fail even when the track is nonlinear or the scanning trace is non-linear, and which is reliable.
A further object of the invention is to provide a digital VTR with which a fast replay is possible at a large number of speeds, and which is convenient to use.
A further object of the invention is to provide a digital VTR with which a fast replay is possible at the same speed without regardless of whether the drum is of two-head configuration or four-head configuration.
A further object of the invention is to provide a digital VTR which permits detection of burst errors at a short processing time using a means of a simple configuration, and detection of erroneous correction.
A further object of the invention is to enable use of a common recording format for the normal data and the fast replay data, and to thereby simplify the format forming means in the recording system and the ID and header reading means in the replay system.
A further object of the invention is to provide a digital VTR with which a fast replay is possible at a plurality of speeds, and the screen is switched at an interval to provide pictures which are easy to see.
A further object of the invention is to provide a device which can record and replay a maximum amount of fast replay signal at each of the fast replay speeds.
A further object of the invention is to provide a device capable of replaying the fast replay signal without being affected by the fluctuation in the head scanning traces.
A further object of the invention is to provide a device capable of fast replay at a very high speed.
According to one aspect of the invention, there is provided a digital VTR for recording recording data having digital video and audio signals, with error correction codes respectively appended in the recording and vertical directions, in respective predetermined areas on oblique tracks of a magnetic recording tape in a predetermined track format, and replaying from the areas, comprising:
data separating means for extracting data of intra encoded blocks in the form of intra-frame or intra-field blocks from the intra-frame or intra-field encoded, or inter-frame or inter-field encoded digital video signal, and the digital audio signal, contained in an input bit stream;
error correction code appending means for appending error correction code to the data of the intra-encoded blocks extracted by said data separating means; and
recording means for recording the data with the error correction code appended, in the recording areas allocated in the magnetic recording tape to special replay data.
With the above arrangement, when replay signal obtained intermittently by scanning the magnetic recording tape during fast replay or slow replay is used to form a replay picture, it is possible to achieve error correction, and accordingly, even for the replay signal having a low output level and a poor symbol error rate, a special replay picture of a satisfactory quality can be formed by applying error correction.
It may so arranged that the recording means disposes the special replay data recording areas in such recording areas that by scanning the magnetic recording tape once with a rotary head at a predetermined replay speed during replay of the special replay data, the error correction code can be reconstructed.
With the above arrangement, the capacity of the memory required in the error correction decoder for forming an error correction block can be reduced. Moreover, the timings for control over writing and reading of the replay data into or from the memory, and starting the error correction can be synchronized with the rotation of the rotary head, so that the control over the memory and control over the error correction decoder can be simplified, and the overall circuit size can be reduced.
It may so arranged that the recording means disposes the special replay data recorded on the magnetic recording tape, taking error correction block for the respective replay speed as a unit, in recording areas concentrated on oblique tracks of the magnetic recording tape.
With the above arrangement, even where there is non-linearity in the track, its effect can be avoided, and the special replay data can be reconstructed without being influenced by the non-linearity, and a special replay picture of a good quality can be obtained.
It may be so arranged that the error correction code appending means appends, to the special replay data, error correction code set to have a minimum distance identical to that of error correction code appended to the digital video or audio signal.
With the above arrangement, by slightly modifying the error correction decoder for the digital video signal or the digital audio signal, error correction decoding can be achieved, and it is not necessary to add a separate error correction decoder, so that the circuit size can be reduced.
It may be so arranged that the error correction code appending means appends, to the intra-encoded block, error correction code having identical magnitude for each of the replay speeds.
With the above arrangement, special replay data can be decoded using the same error correction decoder for various replay speeds, and the circuit size can be reduced.
It may be so arranged that the recording means disposes the error correction code in such recording areas that by scanning the magnetic recording tape once with a rotary head at a predetermined positive or negative symmetrical replay speed (which may be either of the values corresponding to positive and negative tape transport speeds having the same absolute value) during replay of the special replay data, the error correction code can be reconstructed.
With the above arrangement, maximum use is made of the special replay data recording areas to form error correction blocks. Moreover, it is possible to avoid repetition of the special replay data more than necessary, and the sizes of the error correction blocks for the respective replay speeds can be made uniform, and the overall circuit size can be reduced.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals in respective predetermined areas on oblique tracks of a magnetic recording tape in a predetermined track format, and replaying from the areas, comprising:
data separating means for extracting intra-encoded data in the form of intra-frame or intra-field data from the intra-frame or intra-field encoded, or inter-frame or inter-field encoded digital video signal
the intra-frame or intra-field digital video signal, and the digital audio signals, contained in an input bit stream;
recording means for recording the bit stream in areas for the digital video signal, and recording the intra-encoded data extracted at the data separating means, in areas for the digital audio signal.
With the above arrangement, the intra-frame or intra-field, and inter-frame and inter-field encoded digital video signal and the digital audio signal are input in the form of a bit stream, and the bit stream is recorded in the digital video areas, while the extracted intra-frame or intra-field encoded data only is also recorded in the digital audio areas. In this way, the still replay data and slow replay data are formed.
It may be so arranged that the data separating means extracts the intra-frame or intra-field encoded data packet by packet from the bit stream in which the digital video and audio signals are mixed in the form of packets of respectively constant lengths.
With the above arrangement, intra-frame or intra-field encoded data is extracted packet by packet from the bit stream in which the digital video and audio signals are mixed in the form of packets of respectively constant lengths, so that the still replay data and slow replay data can be separated packet by packet. Accordingly, the bit stream can be recorded without modification, on the magnetic tape.
It may be so arranged that the data separating means extracts the intra-frame or intra-field data macro block by macro block from the bit stream forming the digital video data of one macro block, having a plurality of luminance signal blocks and chrominance signal blocks collectively, each block consisting of 8 pixels by 8 lines.
With the above arrangement, intra-frame or intra-field data is extracted macro block by macro block, so that the still replay data and the slow replay data can be separated macro block by macro block. It is therefore possible to cope with the data, formed taking a macro block as a unit, such as that of progressive refreshing.
The digital VTR may further comprise memory means for storing one frame of field of the intra encoded data extracted by said data separating means, data being read from said memory means at a data rate at which data is recorded in the digital audio signal areas.
With the above arrangement, at least one frame or field of intra encoded data is sequentially written, and read at a data rate at which it is recorded in the digital audio signal areas, so that the data is extracted frame by frame or field by field. Accordingly, a still picture can always be recorded by extracting the data frame by frame or field by field.
The digital VTR may further comprises picture replay means for replaying video data for special replay, such as fast replay, still replay, and slow replay, from the intra-encoded data recorded in the digital audio signal areas.
With the above arrangement, by replaying video data for special replay, such as fast replay, still replay and slow replay, pictures with a high definition can be produced.
According to another aspect of the invention, there is provided a digital VTR for recording recording digital video and audio signals in respective designated areas of oblique tracks in a predetermined track format, and replaying from the areas, comprising:
data separating means for extracting intra-encoded data in the form of intra-frame or intra-field encoded data from the intra-frame or intra-field encoded, or inter-frame or inter-field encoded digital video signal, and the digital audio signal contained in an input bit stream; and
recording means for recording the bit stream in the digital video signal areas, and recording the intra-encoded data extracted by the data separating means in the digital audio signal areas, and in the digital video signal areas.
With the above arrangement, the input bit stream is recorded in the digital video areas, and the intra-frame or intra-field encoded data extracted from the bit stream is recorded in the digital video signal areas and the digital audio signal areas, so that by using both of the digital video signal areas and the digital audio signal areas, special replay data with a good picture quality can be obtained.
It may be so arranged that the recording means records a first low-frequency component of the intra-frame or intra-field encoded data in the digital video signal areas, and records a second low-frequency component of a higher-frequency band than the first low-frequency component, of the intra-frame or intra-field decoded data, in the digital audio signal areas.
With the above arrangement, the first low-frequency component of the intra-frame or intra-field encoded data is recorded in the digital video signal areas, and the second low-frequency component of a higher-frequency band than the first low-frequency component is recorded in the digital audio signal areas. Accordingly, a better picture quality can be obtained, and the special replay image can be obtained even if the data in the digital audio signal areas is not reproduced.
According to another aspect of the invention, there is provided a digital VTR for recording recording digital video and audio signals in respective designated areas of oblique tracks in a predetermined track format, using a rotary drum on which head of two different azimuths are mounted, comprising:
data separating means for extracting a fast replay signal from the normal recording signal;
recording means for recording the fast replay signal in one region in one track per one scanning of the head, of the regions covered by the head traces and in the tracks of identical azimuth;
identification signal recording means for recording an identification signal for identifying the track; and
replay means for replaying the identification signal.
With the above arrangement, the fast replay data can be reproduced from one location in one track per one scanning of the head during fast replay, so that even when the track is non-linear or the scanning trace is non-linear, the head can be scanned with reference to the region at said location where the fast replay data is recorded, and the data can be accurately reproduced.
It may be so arranged that a first recording region is provided in one track of one azimuth in which the fast replay signal is recorded, and a second recording region for recording the fast replay signal is also provided in the track of the other azimuth, and succeeding said one track;
the length of the second recording region is about half the length of the first recording region, and the center of the second recording region within the track is at about the same position as the center of the first recording region within the track.
With the above arrangement, in the case of a drum of two-head configuration, the fast replay signal in the tracks of one azimuth can be reproduced from the first recording region, while in the case of four-head configuration, the fast replay signal in the tracks of both azimuths can be reproduced from the first and second recording regions. As a result, the total amount of fast replay data, given as the sum of the data from the heads of two different azimuths, is the same, and the screen (whole picture) can be formed from the same amount of fast replay data, regardless of the head configuration, during fast replay at the same speed.
As a result, it is possible to obtain a device with which the fast replay speed is not limited by the head configuration, and the fast replay picture quality is identical regardless of the head configuration, and the device is therefore convenient to use.
It may be so arranged that, in the upper and lower end parts of the first recording region which extend out of the region corresponding to the second recording region of the adjacent track of a different azimuth, the signal identical to those in said second recording region is recorded.
With the above arrangement, where the sub-regions formed by equally dividing the first recording region is called A1, A2, A3 and A4, in turn, the signals recorded in the regions A1 and A4 are extracted, and recorded, without modification, in the second recording region, as well. In other words, the fast replay data recorded in the track of a first azimuth is divided equally and the first and fourth quarter data are recorded in the track of a succeeding, second azimuth. The data recorded in the track of the second azimuth can therefore be obtained by simple rearrangement means.
It may be so arranged that the recording means forms the fast replay signal dedicated for the particular fast replay signal for each of the fast replay speeds, and records the fast replay signal at different positions on the magnetic recording tape.
With the above arrangement, the fast replay signals are prepared for the respective fast replay speeds, and the data is configured so that the picture is switched at an interval which facilitates watching of the reproduced picture during fast replay at each speed.
It may be so arranged that the recording means repeatedly records the fast replay signal for (M×i)-time speed replay (i=1, 2, . . . n) at predetermined positions in predetermined tracks of consecutive M (M being a natural number) tracks, and repeatedly records the fast replay signal for (M×i)-time speed replay, 2×i times, taking the M tracks as one unit for each speed.
With the above arrangement, the fast replay signal for the predetermined speed is recorded in the predetermined position in the predetermined track, of the consecutive M tracks, and the fast replay signal for the (M×n)-time speed replay is repeatedly recorded 2n times, taking the M tracks as a unit. Accordingly, during fast replay, it is sufficient if the control over the drum rotation and the tape transport speed performed in such a manner that the fast replay signal recorded at one location in the M tracks is reproduced. For instance, when the fast replay is effected at (M×n)-time speed, compared with the case in which the fast replay data is recorded at one location in M×n tracks, the amount of movement to a predetermined track in the state of transition at the time of changing the replay speed is smaller, and the reproduction of the fast replay data at the newly selected speed can be started in a shorter time.
It may be so arranged that the recording means repeatedly records the fast replay signal for 4i-time speed replay (i=1, 2, . . . n) at predetermined positions in predetermined tracks of consecutive four (M being a natural number) tracks, and
said identification signal recording means records three types of frequency signals as pilot signal for tracking control on these four tracks, being in superimposition with the digital data.
With the above arrangement, the fast replay data is disposed taking four tracks as a unit, and the identification signals (such as the three pilot signals f0, f1 and f2 two of which (f1 and f2) may consist of two different frequency signals superimposed on the digital data signal, and the last one of which (f0) may be featured by the absence of any signal superimposed on the digital data signal) for tracking control are recorded, so that, during fast replay, by the use of the identification signal, the desired track can be selected, and the fast replay data recorded in the track can be reproduced.
It may be so arranged that the digital VTR further comprises error correction code appending means for appending the error correction code formed of a predetermined number of sync bits inserted at a predetermined period in the signal sequence recorded in the magnetic recording tape, a predetermined number of ID bits succeeding the sync bits, a predetermined number of first parity bits generated from the ID bits, second parity bits generated from a predetermined number of digital data succeeding the first parity bits, third parity bits generated from a plurality of digital data extending over the sync bits, and fourth parity bits generated from the digital data and positioned at the back of the digital data;
erroneous correction detection means for comparing the fourth parity bits with the first parity bits reproduced by the replay means, and detecting erroneous correction on the basis of the result of comparison.
With the above arrangement, a fourth parity is appended only to the digital data recorded in the sync blocks, and on the basis of the result of the fourth parity check, the burst error in which the digital data is continuously missing in the middle of it can be detected quickly by a relatively simple comparison means.
Moreover, on the basis of such information, the erroneous correction at the error correction decoder in a replay system at the next stage can be detected.
It may be so arranged that the error correction code appending means appends the fourth parity bits only to the fast replay signal.
With the above arrangement, errors can be detected promptly even in a fast replay in which burst errors occur frequently due to the periodical amplitude fluctuation in the replay signal.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals, in designated areas on oblique tracks of a magnetic recording tape, in a predefined format, using a rotary drum on which heads of two different azimuths are mounted, and replaying from the areas, comprising:
data separating means for extracting digital video signal (hereinafter referred to as fast replay signal) used for fast replay, from a normal recording signal;
recording means for recording the fast replay signals for the respective fast replay speeds, in predefined consecutive regions in a predefined track of a group of four consecutive tracks;
identification signal recording means for recording identification signal for identifying the tracks;
replay means for replaying the recording signal for normal replay, or fast replay signals for +2-time speed replay, or +4N-time speed replay or (−4N+2)time speed replay (N being a positive integer); and
tracking control means for performing tracking control so that the head scans the predefined regions in the predefined track of the four tracks in accordance with the identification signal.
With the above arrangement, four tracks are taken as a unit, and identical pattern is repeated every four tracks, and the data for each fast replay speed is recorded in the specific consecutive sync blocks in specific track, and during fast replay, the tracking is controlled at the specific position on the specific track. As a result, it is possible to increase the recording rate of the fast replay data.
It may be so arranged that the identification signal recording means comprises:
recording means for recording, as said identification signal, pilot signals of two different frequencies alternately, every other tracks; and
the tracking control means includes comparison means for comparing the levels of the identification signals of the two different frequencies contained in the replay signal, while the head is scanning the position corresponding to the center of the area where the fast replay signal for the particular fast replay speed is recorded.
With the above arrangement, during fast replay, by comparing, at a specific timing, the levels of the identification signals of two different frequencies contained in the replay signal, and effecting tracking control on the basis of the result of the comparison, the head scans the areas where the data for the respective fast replay speed is recorded. As a result, even if the there is nonlinearity in the track, or the like, it is possible to accurately track the region where the necessary data is recorded.
It may be so arranged that the identification signal recording means comprises:
recording means for recording, as said identification signal, pilot signals of two different frequencies alternately, every other tracks; and
the recording means records sync block numbers together with the fast replay signal;
the tracking control means compares the levels of the identification signals of of the two different frequencies contained in the replay signal, when the sync block number of the predefined sync block in the area where the fast replay speed signal for the particular fast replay speed is recorded, to achieve tracking control.
With the above arrangement, when the predefined sync block number is detected during fast replay, the levels of the identification signals of two different frequencies are compared, to detect the tracking error, and tracking is controlled on the basis of the result of the comparison, i.e. on the basis of the detected tracking error. Accordingly, the head accurately scans the area where the fast replay data is recorded. That is, even if the position at which the fast replay data is recorded is shifted in the longitudinal direction of the tape, the area where the necessary data is recorded can be tracked accurately.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals, in designated areas on oblique tracks of a magnetic recording tape, in a predefined format, using a rotary drum on which heads of two different azimuths are mounted, and replaying from the areas, comprising:
data separating means for extracting digital video signal (hereinafter referred to as fast replay signal) used for fast replay, from a normal recording signal;
appending means for appending sync byte, ID byte, header byte to the fast replay signal, in the same sync block configuration as said recording signal;
recording means for recording the fast replay signal in areas on tracks, such that during fast replay, only one location on one track of an azimuth identical to the head is covered by the head scanning trace;
identification signal recording means for recording identification signal for identifying the tracks; and
replay means for replaying the identification signal.
With the above arrangement, the areas where normal replay data is recorded, and the areas where fast replay data is recorded have an identical sync block configuration, (with identical sync, ID and header configurations) so that the appending means for appending sync byte, ID byte and header byte in the recording system, and the reading means (including the ID and header reading means) can be used in common.
The digital VTR may further comprise:
input means for inputting a password from outside;
recording means for recording the password together with the digital video signal;
replay means for replaying the password at the time of replay of the digital video signal; and
replay inhibiting means for inhibiting display of the digital video signal unless a correct password is input at the time of replay.
With the above arrangement, it is possible to protect the program or the whole tape from unauthorized replay.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals, in designated areas on oblique tracks of a magnetic recording tape, in a predefined format, using a rotary drum on which heads of two different azimuths are mounted, and replaying from the areas, comprising:
data separating means for extracting digital video signal (hereinafter referred to as fast replay signal) used for fast replay, from a normal recording signal;
recording means for disposing a fast replay signal for an (M×i)-time speed replay (i=1, 2, . . . , n), at predefined positions on predefined tracks of consecutive M tracks (M being a natural number), and repeatedly recording the fast replay signal for (M×i)-time speed replay, (2×i) times;
identification signal recording means for recording identification signal for identifying the tracks on which the fast replay signal is recorded; and
replay means for performing replay at an arbitrary replay speed which is an even-number of times the normal speed, and is lower than the (M×n)time speed, using the fast replay signal recorded for (M×n)-time speed replay.
With the above arrangement, the data recorded for (M×n)-time speed replay can be all replayed at an even-multiple speed lower than the (M×n)time speed, although the reproduced data may be duplicated.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals, in designated areas on oblique tracks of a magnetic recording tape, in a predefined format, using a rotary drum on which heads of two different azimuths are mounted, and replaying from the areas, comprising:
data separating means for extracting intra-frame encoded image data, from an input bit stream;
recording means for forming fast replay signals for a plurality of fast replay speeds from the image data, and recording the n1-time fast speed signal in an area therefor, at positions designated according to the corresponding position on the screen of the signals, with the signals corresponding to the edges of the screen being positioned at the ends of the recording region on the oblique track, and with the signals corresponding to the position toward the center of the screen being positioned toward the center of the recording region on the oblique track; and
replay means for performing fast replay at an n2 time speed (n2>n1) by replaying the n1-time fast replay signal.
With the above arrangement, the fast replay signal of the central part of the screen is collectively recorded in the center of the area recording the n1-time fast replay signal, and replay is conducted at a fast replay speed n2, higher than n1.
Accordingly, although the areas from which the signal is replayed is narrowed because of the increase of the replay speed to n2, the central part of the screen can be replayed.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals, in designated areas on oblique tracks of a magnetic recording tape, in a predefined format, using a rotary drum on which heads of two different azimuths are mounted, and replaying from the areas, comprising:
sync block forming means for forming sync blocks by appending sync bytes to digital signal recorded in the magnetic recording tape at a predetermined interval;
data separating means for extracting a fast replay signal from the normal recording signal;
recording means for sequentially and repeatedly recording n pieces of data Di (i=1, 2, . . . n, n being a natural number) each of which can be recorded in one sync block, over (n+2×w) consecutive sync blocks Sj (j=1, 2, . . . (n+2×w)) at identical positions on predefined tracks;
wherein n is a maximum number of sync blocks which can always be reproduced from the track regions overlapping with the head scanning traces during m-time speed replay,
w is a minimum natural number which is not smaller than the maximum shift from the reference position at which the head crosses a specific track, during m-time speed repay.
With the above arrangement, the maximum amount of data a head can reproduce from one track at a predefined fast replay speed is recorded repeatedly in the vicinity of the head scanning trace, taking account of the head position fluctuation, the maximum amount of data which is recorded can all be reproduced during fast replay. All the data can be read during fast replay in which the effect of the head position fluctuation is large.
It may be so arranged that the recording means repeatedly records the fast replay signal in (n+2×w) consecutive sync blocks Sj at an identical sync block position on each track, on at least m consecutive identical-azimuth tracks.
With the above arrangement, the fast replay signal is repeatedly recorded at identical positions on consecutive tracks, so that the fast replay signal can be replayed whichever track the head begins scanning during fast replay.
Accordingly, control over the head scanning position is simplified, and the fast replay at an arbitrary speed is possible as long as the head passes the predefined track positions.
According to another aspect of the invention, there is provided a digital VTR for recording digital video and audio signals, in designated areas on oblique tracks of a magnetic recording tape, in a predefined format, using a rotary drum on which heads of two different azimuths are mounted, and replaying from the areas, comprising:
sync block forming means for forming sync blocks by appending sync bytes to digital signal recorded in the magnetic recording tape at a predetermined interval;
data separating means for extracting a fast replay signal from the normal recording signal;
recording means for sequentially and repeatedly recording p pieces of data Di (i=1, 2, . . . p, p being a natural number not more than n) each of which can be recorded in one sync block, in (p+L+1) consecutive sync blocks Sj (j=1, 2, . . . (p+L+1)) at the same position in each track, in at least m tracks of consecutive identical-azimuth tracks in such a manner as to satisfyek+1=mod[{ek+p−mod(p+L+1, p)}, p]
where ek and ek+1 (integers not less than 1 and not more than p) are the suffixes i to the data D first recorded,
where n is the maximum number of sync blocks which can always be reproduced consecutively from the region of the track on the tape overlapping with the head scanning trace during m-time speed replay,
L is the number of sync blocks which is a minimum integer not smaller than (D−B+C)
where C is the difference between the starting positions of the tracks Tk and Tk+1 in the track longitudinal direction,
D is the difference between the positions, in the track longitudinal direction, at which the head crosses with the respective tracks,
B is the length of the region from which the reproduction from one track is possible consecutively, during m-time speed replay, and
mod [a, b] expresses the remainder of a divided by b.
With the above arrangement, the arrangement of data repeatedly recorded on the tracks is such that the different data recorded on two identical-azimuth tracks proximate to each other and crossed by the head during one scanning are reproduced at least once without fail, so that the fast replay data can be recorded with a minimum number repetitions. With the arrangement of data described above, even when the head scanning trace position fluctuates or the head trace phase is shifted, reading of the fast replay data is ensured, and images can be reproduced with a good quality, and much fast replay data can be recorded and reproduced.